Yoga means Union, union of the body, mind & soul. In the western world we too often believe yoga to be a series of postures performed to sweat and achieve relaxation, but there is a lot more to it; asanas (postures) are only a piece of the yogic philosophy.
Patanjali, ancient yoga philosopher, identified 8 stages yogis should go through in order to achieve this perfect union. They are also referred to as "the eight limbs of yoga" or "ashtanga" and are a mix of discipline, physical & emotional cleansing and meditation that when practiced lead to a higher conscience and a meaningful liberated life.
Let's take a look at each of them:
This is the first step and it relates directly to our relationship to our environment. It is a set of moral rules towards others and the planet. There are 5:
Ahimsa refers to the principle of non-violence towards others, nature but also ourselves. Relating it to your yoga practice, you should never overdo poses and harm your body.
Satya or truthfulness is the constant effort towards aligning one's thought, speech & action. Here we need to ensure we do not harm people with our words but we should also be our real self rather than associating with our ego-self.
Asteya translates to "non-stealing". Here we should look beyond the mere act of stealing (a bank). It also refers to not stealing other people's time, stealing resources from the planet (taking long showers, over consuming food and clothes...).
Bramacharya often known as sexual restraint: does not mean we should stop sexual activity but rather limit the use of energy, be more present and conscious use of energy.
Aparigraha (non-possessiveness): we should not identify with material possessions, people and ego. We should detach from the results of our actions. On the mat, we should practice yoga consciously, because we enjoy it, without looking to be able to do splits or the hardest pose.
This second step focuses on 5 rules of conduct towards ourselves. The hygiene of our body and mind or inner observances.
Saucha (purity) includes a series of self purification techniques to clean both the body and the mind.
Santosha (contentment): through learning to be content with what we have, we achieve happiness.
Tapas (discipline or austerity): it also means "heat" and its most illustrative form is the practice of asanas requiring discipline. Through physical yoga, heat is generated and a change in the body and mind happens.
Svadhyaya (self study): human beings need to study and know themselves. Not in the psychological way we are used to but rather look for their interior self, the part of our being that does not change and let it shine (what is often referred to as "soul").
Ishvara Pranidhana (constant devotion to God): this last niyama calls for the surrender to a higher self, the recognition that we belong to something bigger.
This third step is also the most famous amongst us. Asana means "posture" and is the physical part of yoga (what we practice when going to a yoga studio). Although we think yoga is exercise to feel and look good, the series of asanas is meant to unable the body to seat in meditation for long hours. By making the body more flexible, we also make the mind more flexible leading us to higher levels of consciousness.
The art of breathing and regulating the flow of energy that emerges from conscious breathing. There exist many yogic breathing exercises aimed at calming, harmonising or elevating the flow of energy within us. These techniques are introduced after some time of practising asanas.
With this fifth step we leave the physical world to go within. Pratyahara is the withdrawal from all senses. We stop all sensory inputs to quiet the mind and look within. Closing our eyes and being in a silent room helps when starting your practice. More advanced yogis can enter pratyahara in the middle of a loud crowd.
Also known as "concentration". Now that we have withdrawn from our senses we can really concentrate and enter this pre-step before getting to meditation. Some can do so by concentrating on breathing, a candle or a mantra. You can also double it by chanting a mantra while counting.
With the seventh stage we enter meditation, that is an absorbed state where the mind is deeply quiet and totally in the present. Most meditation classes are teaching us "dharana", the prior step. Meditation cannot be taught, it is a deeper level one can only achieve when ready, when all the prior limbs have been completed.
Samadi is the eighth and final stage of yoga where we achieve liberation through the union with the soul or divine. Only few people achieve this stage where we are liberated from the ego and we see everything clearly without the filter of our emotions.
If you would like to dive deeper into these 8 limbs of yoga, I recommend the book "The Tree of Yoga" by BKS Iyengar: it is clear, easy to read and nicely illustrated. Iyengar uses the image of a tree to explain the purpose of these 8 stages. Here is the image: